There are many situations in business and industry when it is desirable to provide air which is substantially free of water and water vapor. Such a situation exists for instance, in the plastics industry where the air which is used to convey plastic particles into an extruder may not carry water into the system with it without danger to the apparatus and the operator, as well as the quality of the finished product. Generally speaking, air for this purpose is dried by passing it through a desiccant material and then flows to the storage chamber for the plastic material where it serves to preheat and dry the plastic before it enters the extruder. In the past, once the desiccant has been completely soaked with water, it is necessary to take it out of the apparatus and replace it, or in some other way substitute a dryer with a dry desiccant for the dryer previously used. Attempts to solve this problem have resulted in apparatus which is both complex and expensive and has resulted in equipment which is so large and bulky that it is difficult to move it within a plant from one plastic injection machine to another. These and other difficulties experienced with the prior art devices have been obviated in a novel manner by the present invention.
It is, therefore, an outstanding object of the invention to provide a gas drying apparatus containing two bodies of desiccant which are used alternately to dry and to be dried by flow of air.
Another object of the present invention is the provision of a gas drying apparatus which is small in size and which is portable, so that it can be moved from one location to another.
A further object of the instant invention is the provision of a gas drying apparatus consisting of two desiccating (drying) towers which provide long residence time for air in the desiccant and assures extremely high drying efficiency.
It is another object of the instant invention to provide a gas drying apparatus including two desiccating towers in which one tower is drying, the other is being regenerated.
A still further object of the invention is the provision of a desiccating apparatus of the regenerative type in which automatic equipment brings about the alternating process automatically throughout a plastic drying cycle.
It is a further object of the invention to provide a gas drying apparatus in which dry air is heated to a preset selected temperature and delivered to a machine-mounted plenum drying hopper to dry plastic.
It is a still further object of the present invention to provide a gas drying apparatus having mechanism that is readily accessible for repair and maintenance.
With these and other objects in view, as will be apparent to those skilled in the art, the invention resides in the combination of parts set forth in the specification and covered by the claims appended hereto.